Natural History of IntraDiscal Vacuum Phenomenon and its role in Advanced Disc Degeneration.

STUDY DESIGN:Observational serial CT analysis of the lumbar spine in a normal-aging population. OBJECTIVE:Assess the natural history of IntraDiscal Vacuum Phenomenon and its role in disc degeneration. Summary of Background Data: The natural history of disc degeneration is well described but our understanding of the end stage of pathogenesis remains incomplete. MRI loses accuracy with advanced degeneration, becoming hyporesonant and indistinct. Cadaveric specimens display adaptive changes in the disc with loss of the hydrostatic capacity of the nucleus, increased intra-discal clefts and end-plate impermeability. IDVP is associated with advanced disc degeneration and CT is the optimal modality to visualise this, yet these insights remain unreported. METHODS:Subjects only included historic CT abdomen scans of those over 60 years of age without acute or relevant spinal pathology, with a diagnosis of at least one level with IDVP on the original CT scan and all of whom had a similar scan >7 years later. A history of clinically significant back pain was also recorded. RESULTS:CT scans included 360 levels in 29 males and 31 females (mean 68.9 years), displaying 82 levels of IDVP, with a second scan included after a mean of 10.3 years, Most levels displayed the same level of severity (persisted, 45) compared to where some progressed (26), regressed (8) and fused (3) (P<0.01). There was also an increased incidence, 37/60 (62%) of developing IDVP at another level. Disc heights were reduced with increased severity of IDVP. A record of back pain was evident in 31/60 subjects, which was not significantly worse in those with worsening severity or additional level involvement over the study period. CONCLUSION:As disc degeneration advances, the associated IDVP persists in most cases, displaying a plateauing of severity over long periods, but rarely with progression to autofusion.